1jpn: Difference between revisions
New page: left|200px<br /><applet load="1jpn" size="450" color="white" frame="true" align="right" spinBox="true" caption="1jpn, resolution 1.90Å" /> '''GMPPNP Complex of SR... |
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[[Image:1jpn.gif|left|200px]]<br /><applet load="1jpn" size=" | [[Image:1jpn.gif|left|200px]]<br /><applet load="1jpn" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1jpn, resolution 1.90Å" /> | caption="1jpn, resolution 1.90Å" /> | ||
'''GMPPNP Complex of SRP GTPase NG Domain'''<br /> | '''GMPPNP Complex of SRP GTPase NG Domain'''<br /> | ||
==Overview== | ==Overview== | ||
BACKGROUND: The signal recognition particle (SRP) is a phylogenetically | BACKGROUND: The signal recognition particle (SRP) is a phylogenetically conserved ribonucleoprotein that mediates cotranslational targeting of secreted and membrane proteins to the membrane. Targeting is regulated by GTP binding and hydrolysis events that require direct interaction between structurally homologous "NG" GTPase domains of the SRP signal recognition subunit and its membrane-associated receptor, SR alpha. Structures of both the apo and GDP bound NG domains of the prokaryotic SRP54 homolog, Ffh, and the prokaryotic receptor homolog, FtsY, have been determined. The structural basis for the GTP-dependent interaction between the two proteins, however, remains unknown. RESULTS: We report here two structures of the NG GTPase of Ffh from Thermus aquaticus bound to the nonhydrolyzable GTP analog GMPPNP. Both structures reveal an unexpected binding mode in which the beta-phosphate is kinked away from the binding site and magnesium is not bound. Binding of the GTP analog in the canonical conformation found in other GTPase structures is precluded by constriction of the phosphate binding P loop. The structural difference between the Ffh complex and other GTPases suggests a specific conformational change that must accompany movement of the nucleotide from an "inactive" to an "active" binding mode. CONCLUSIONS: Conserved side chains of the GTPase sequence motifs unique to the SRP subfamily may function to gate formation of the active GTP bound conformation. Exposed hydrophobic residues provide an interaction surface that may allow regulation of the GTP binding conformation, and thus activation of the GTPase, during the association of SRP with its receptor. | ||
==About this Structure== | ==About this Structure== | ||
1JPN is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermus_aquaticus Thermus aquaticus] with CA, GNP and ACY as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | 1JPN is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermus_aquaticus Thermus aquaticus] with <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=GNP:'>GNP</scene> and <scene name='pdbligand=ACY:'>ACY</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1JPN OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Thermus aquaticus]] | [[Category: Thermus aquaticus]] | ||
[[Category: Freymann, D | [[Category: Freymann, D M.]] | ||
[[Category: Padmanabhan, S.]] | [[Category: Padmanabhan, S.]] | ||
[[Category: ACY]] | [[Category: ACY]] | ||
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[[Category: srp54]] | [[Category: srp54]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:25:19 2008'' | ||
Revision as of 14:25, 21 February 2008
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GMPPNP Complex of SRP GTPase NG Domain
OverviewOverview
BACKGROUND: The signal recognition particle (SRP) is a phylogenetically conserved ribonucleoprotein that mediates cotranslational targeting of secreted and membrane proteins to the membrane. Targeting is regulated by GTP binding and hydrolysis events that require direct interaction between structurally homologous "NG" GTPase domains of the SRP signal recognition subunit and its membrane-associated receptor, SR alpha. Structures of both the apo and GDP bound NG domains of the prokaryotic SRP54 homolog, Ffh, and the prokaryotic receptor homolog, FtsY, have been determined. The structural basis for the GTP-dependent interaction between the two proteins, however, remains unknown. RESULTS: We report here two structures of the NG GTPase of Ffh from Thermus aquaticus bound to the nonhydrolyzable GTP analog GMPPNP. Both structures reveal an unexpected binding mode in which the beta-phosphate is kinked away from the binding site and magnesium is not bound. Binding of the GTP analog in the canonical conformation found in other GTPase structures is precluded by constriction of the phosphate binding P loop. The structural difference between the Ffh complex and other GTPases suggests a specific conformational change that must accompany movement of the nucleotide from an "inactive" to an "active" binding mode. CONCLUSIONS: Conserved side chains of the GTPase sequence motifs unique to the SRP subfamily may function to gate formation of the active GTP bound conformation. Exposed hydrophobic residues provide an interaction surface that may allow regulation of the GTP binding conformation, and thus activation of the GTPase, during the association of SRP with its receptor.
About this StructureAbout this Structure
1JPN is a Single protein structure of sequence from Thermus aquaticus with , and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
The conformation of bound GMPPNP suggests a mechanism for gating the active site of the SRP GTPase., Padmanabhan S, Freymann DM, Structure. 2001 Sep;9(9):859-67. PMID:11566135
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